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Re: ntp issue on linux server, time goes ahead

 
AVV
Super Advisor

ntp issue on linux server, time goes ahead

Hi All,

I am using a BL 460c blade for a linux (rhel 5.3 64bit)host and an oracle dbase runs in. I am facing an issue with the timing now. If I am restarting the ntpd service, time sync with the server but slowly it goes ahead upto 10 min in two weeks which makes my database screwed. All other server connected to my time server is working well. I have given few outputs below. Please help me in this.

[root@prodsrvr log]# dig timesrv.dc

; <<>> DiG 9.3.4-P1 <<>> timesrv.dc
;; global options: printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NXDOMAIN, id: 20578
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 0

;; QUESTION SECTION:
;timesrv.dc. IN A

;; AUTHORITY SECTION:
. 10759 IN SOA a.root-servers.net. nstld.verisign-grs.com. 2010072001 1800 900 604800 859

;; Query time: 0 msec
;; SERVER: 192.168.0.20#53(192.168.0.20)
;; WHEN: Tue Jul 20 23:38:40 2010
;; MSG SIZE rcvd: 108


[root@prodsrvr log]# nslookup timesrv.dc.com
Server: 192.168.0.20
Address: 192.168.0.20#53

Name: timesrv.dc.com
Address: 192.168.0.20


[root@prodsrvr log]#
[root@prodsrvr log]# ntpq -p
remote refid st t when poll reach delay offset jitter
==============================================================================
timesrv.dc .LOCL. 1 u 20 64 377 0.248 -268.90 136.550
[root@prodsrvr log]#
12 REPLIES 12
Tim Nelson
Honored Contributor

Re: ntp issue on linux server, time goes ahead

Is ntpd running ?

service ntpd status



AVV
Super Advisor

Re: ntp issue on linux server, time goes ahead

Hi,

ntpd is running. I have confirmed that first.

#service ntpd status
ntpd (pid 11107) is running...
Wilfred Chau_1
Respected Contributor

Re: ntp issue on linux server, time goes ahead

How come timesrv.dc.com resolves to an 192.168.0.0 IP ? Does it connect to an external NTP source?

Try change your ntp to use a public NTP server nearest to your machine from this url:
http://support.ntp.org/bin/view/Servers/NTPPoolServers


Matti_Kurkela
Honored Contributor

Re: ntp issue on linux server, time goes ahead

If there is no asterisk (*) in the first column in the "ntpq -p" output, the ntpd service has _not_ synchronized with a NTP server, so it cannot correct the system clock effectively.

Your offset value (estimated difference of the time value between your ntpd and the NTP server) is -268.90 ms: this is currently too much. For successful synchronization, the offset would have to be smaller than 128 ms (positive or negative).

The root cause for non-synchronization is probably the high jitter: if the round-trip delay in the communication between ntpd and the NTP server has more than about 100 ms of jitter, ntpd will drop out of sync so often that it will be almost useless. (The NTP documentation says the jitter value is an exponentially weighted root-mean-square average deviation from the average delay.)

In practice, the large jitter value means that the travel time of the NTP time message from the NTP server to your ntpd is not predictable enough. Jitter usually becomes high when you're trying to synchronize time over a very congested/overloaded network connection.

If you have other servers connected to the same switch as this BL460c blade, the congested connection might be the one between the blade and the switch. If possible, you should take a look at the switch port statistics and find out how busy the blade's network interfaces are.

If you have only one active network interface, consider setting up bonding to get more network bandwidth to your blade.

MK
MK
bullz
Super Advisor

Re: ntp issue on linux server, time goes ahead

I had the similar problem.

It's a VM?

If so, please login to your VC console and check the time at your VC console

It might help you.
AVV
Super Advisor

Re: ntp issue on linux server, time goes ahead

This is not a VM but a physical blade server BL 460c
John Guster
Trusted Contributor

Re: ntp issue on linux server, time goes ahead

what is the content of the file /etc/ntp.conf?
Ricky_HK
Frequent Advisor

Re: ntp issue on linux server, time goes ahead

For me, I don't use NTP service.
Just add /usr/sbin/ntpdate -s to root crontab, let cron run it one or more times everyday... simple and easy.
Elmar P. Kolkman
Honored Contributor

Re: ntp issue on linux server, time goes ahead

You should try to setup a better NTP network. Have multiple servers (peers) use their clocks to provide the time to the rest of the network and let all other machines on your network use multiple NTP servers for time synchronisation, so that the best server is chosen.

Also have you own local clock in the ntp.conf (server 127.127.1.1).
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